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From "Christopher Tubbs (JIRA)" <j...@apache.org>
Subject [jira] [Reopened] (ACCUMULO-267) Mapreduce API should not use JobContext to set configuration information
Date Thu, 20 Sep 2012 17:22:07 GMT

     [ https://issues.apache.org/jira/browse/ACCUMULO-267?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Christopher Tubbs reopened ACCUMULO-267:
----------------------------------------


This is the wrong way to go about doing this fix. The reason why it took a JobContext is so
that it could accept a "Job" object. This was modeled after the pattern Hadoop was using for
FileOutputFormat, which is somewhat the standard for conventions in configuring MR jobs.

While JobContext does specifically state that's what it's purpose is, it is a base class,
and Job extends JobContext, and includes a comment that describes it as holding the state
of the job at submission time. This API should really be taking a "Job" object, rather than
a "JobContext" object. Further, because Job is the only JobContext that actually works as
intended here, the change from JobContext to Job does not require any deprecation, because
Job will still work, and any other JobContext that isn't a Job will still fail. (We *would*
have to deprecate the ones that were added in 1.4 that took a Configuration object, though...
because those were never "correct", if we are going off of the conventions set by Hadoop's
provided OutputFormats).

It is somewhat annoying to deprecate something in 1.5 that was added in 1.4... especially
since it allows people to go back to what they were doing before. But, I think it might be
worth it to be consistent with the established conventions, and to clarify the semantics of
the methods (we are, after all, modifying the state of a job we are about to submit, and not
just an arbitrary configuration, which is used for all sorts of things).
                
> Mapreduce API should not use JobContext to set configuration information
> ------------------------------------------------------------------------
>
>                 Key: ACCUMULO-267
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-267
>             Project: Accumulo
>          Issue Type: Bug
>          Components: client
>            Reporter: John Vines
>            Assignee: John Vines
>              Labels: mapreduce
>             Fix For: 1.5.0
>
>
> JobContext specifically says that it is a read-only view of job information. Our inputformat's
configuration calls take JobContext as an input, rip out the Configuration object, and writes
to it.
> Instead, calls should just take in a Configuration object directly (or a Job object,
but that passes in more information than is needed, and can cause discrepancies depending
on which mapreduce api).

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